NEW YORK (CNN) --A federal group investigating the collapse of the World Trade Center on September 11, 2001, announced Wednesday it is seeking information from individuals who were inside the Twin Towers that day, or who were in contact with friends and relatives in the buildings.

Within a month, investigators from the National Institute of Standards and Technology (NIST), an arm of the Commerce Department, plan to begin conducting hundreds of interviews either face-to-face, by phone, or through focus groups.

They hope to get firsthand accounts of what was happening inside the towers after they were hit by hijacked airliners.

"These are just a few of the myriad of tiny details that will help us piece together a mosaic that will help us answer the difficult questions of how the buildings failed, and what can be done to reduce future risks from fire or other building emergencies," said Jack Snell, the director of the NIST building and fire research laboratory.

NIST wants to talk to people who were near the floors that were hit or who were in elevators or lobbies, as well as first responders and people who were in contact with family members who worked above the floors of impact.

Interviewers will ask participants to recount their experiences on that day, the actions they took and the information they received.

Through these first-person accounts, NIST hopes to understand how the evacuation and communication system worked, and how people inside the building reacted to the emergency.

These interviews will enhance the data that NIST has already received as part of its 24-month, $16 million investigation into the structural failure and collapse of several WTC buildings.

NIST has collected more than 5,600 photos and over 4,600 video clips that have helped the organization understand how the fire grew and spread through the buildings, but investigators hope the interviews will help fill in the gaps, such as what kinds of damage or fire people saw, what sounds they heard, and what barriers and difficulties they encountered.

Nearly 2,800 people -- both inside the buildings and on the two planes -- died in the attacks.